﻿//-----------------------------------------------------------------------
// <copyright file="SingleInstance.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <summary>
//     This class checks to make sure that only one instance of 
//     this application is running at a time.
// </summary>
//-----------------------------------------------------------------------

namespace AppTemplate
{
   using System;
   using System.Collections;
   using System.Collections.Generic;
   using System.ComponentModel;
   using System.IO;
   using System.Runtime.InteropServices;
   using System.Runtime.Remoting;
   using System.Runtime.Remoting.Channels;
   using System.Runtime.Remoting.Channels.Ipc;
   using System.Runtime.Serialization.Formatters;
   using System.Security;
   using System.Threading;
   using System.Windows;
   using System.Windows.Threading;

   internal enum WM
   {
      NULL = 0x0000,
      CREATE = 0x0001,
      DESTROY = 0x0002,
      MOVE = 0x0003,
      SIZE = 0x0005,
      ACTIVATE = 0x0006,
      SETFOCUS = 0x0007,
      KILLFOCUS = 0x0008,
      ENABLE = 0x000A,
      SETREDRAW = 0x000B,
      SETTEXT = 0x000C,
      GETTEXT = 0x000D,
      GETTEXTLENGTH = 0x000E,
      PAINT = 0x000F,
      CLOSE = 0x0010,
      QUERYENDSESSION = 0x0011,
      QUIT = 0x0012,
      QUERYOPEN = 0x0013,
      ERASEBKGND = 0x0014,
      SYSCOLORCHANGE = 0x0015,
      SHOWWINDOW = 0x0018,
      ACTIVATEAPP = 0x001C,
      SETCURSOR = 0x0020,
      MOUSEACTIVATE = 0x0021,
      CHILDACTIVATE = 0x0022,
      QUEUESYNC = 0x0023,
      GETMINMAXINFO = 0x0024,

      WINDOWPOSCHANGING = 0x0046,
      WINDOWPOSCHANGED = 0x0047,

      CONTEXTMENU = 0x007B,
      STYLECHANGING = 0x007C,
      STYLECHANGED = 0x007D,
      DISPLAYCHANGE = 0x007E,
      GETICON = 0x007F,
      SETICON = 0x0080,
      NCCREATE = 0x0081,
      NCDESTROY = 0x0082,
      NCCALCSIZE = 0x0083,
      NCHITTEST = 0x0084,
      NCPAINT = 0x0085,
      NCACTIVATE = 0x0086,
      GETDLGCODE = 0x0087,
      SYNCPAINT = 0x0088,
      NCMOUSEMOVE = 0x00A0,
      NCLBUTTONDOWN = 0x00A1,
      NCLBUTTONUP = 0x00A2,
      NCLBUTTONDBLCLK = 0x00A3,
      NCRBUTTONDOWN = 0x00A4,
      NCRBUTTONUP = 0x00A5,
      NCRBUTTONDBLCLK = 0x00A6,
      NCMBUTTONDOWN = 0x00A7,
      NCMBUTTONUP = 0x00A8,
      NCMBUTTONDBLCLK = 0x00A9,

      SYSKEYDOWN = 0x0104,
      SYSKEYUP = 0x0105,
      SYSCHAR = 0x0106,
      SYSDEADCHAR = 0x0107,
      COMMAND = 0x0111,
      SYSCOMMAND = 0x0112,

      MOUSEMOVE = 0x0200,
      LBUTTONDOWN = 0x0201,
      LBUTTONUP = 0x0202,
      LBUTTONDBLCLK = 0x0203,
      RBUTTONDOWN = 0x0204,
      RBUTTONUP = 0x0205,
      RBUTTONDBLCLK = 0x0206,
      MBUTTONDOWN = 0x0207,
      MBUTTONUP = 0x0208,
      MBUTTONDBLCLK = 0x0209,
      MOUSEWHEEL = 0x020A,
      XBUTTONDOWN = 0x020B,
      XBUTTONUP = 0x020C,
      XBUTTONDBLCLK = 0x020D,
      MOUSEHWHEEL = 0x020E,


      CAPTURECHANGED = 0x0215,

      ENTERSIZEMOVE = 0x0231,
      EXITSIZEMOVE = 0x0232,

      IME_SETCONTEXT = 0x0281,
      IME_NOTIFY = 0x0282,
      IME_CONTROL = 0x0283,
      IME_COMPOSITIONFULL = 0x0284,
      IME_SELECT = 0x0285,
      IME_CHAR = 0x0286,
      IME_REQUEST = 0x0288,
      IME_KEYDOWN = 0x0290,
      IME_KEYUP = 0x0291,

      NCMOUSELEAVE = 0x02A2,

      DWMCOMPOSITIONCHANGED = 0x031E,
      DWMNCRENDERINGCHANGED = 0x031F,
      DWMCOLORIZATIONCOLORCHANGED = 0x0320,
      DWMWINDOWMAXIMIZEDCHANGE = 0x0321,

      #region Windows 7
      DWMSENDICONICTHUMBNAIL = 0x0323,
      DWMSENDICONICLIVEPREVIEWBITMAP = 0x0326,
      #endregion

      USER = 0x0400,

      // This is the hard-coded message value used by WinForms for Shell_NotifyIcon.
      // It's relatively safe to reuse.
      TRAYMOUSEMESSAGE = 0x800, //WM_USER + 1024
      APP = 0x8000,
   }

   [SuppressUnmanagedCodeSecurity]
   internal static class NativeMethods
   {
      /// <summary>
      /// Delegate declaration that matches WndProc signatures.
      /// </summary>
      public delegate IntPtr MessageHandler(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled);

      [DllImport("shell32.dll", EntryPoint = "CommandLineToArgvW", CharSet = CharSet.Unicode)]
      private static extern IntPtr _CommandLineToArgvW([MarshalAs(UnmanagedType.LPWStr)] string cmdLine, out int numArgs);


      [DllImport("kernel32.dll", EntryPoint = "LocalFree", SetLastError = true)]
      private static extern IntPtr _LocalFree(IntPtr hMem);


      public static string[] CommandLineToArgvW(string cmdLine)
      {
         IntPtr argv = IntPtr.Zero;
         try
         {
            int numArgs = 0;

            argv = _CommandLineToArgvW(cmdLine, out numArgs);
            if (argv == IntPtr.Zero)
            {
               throw new Win32Exception();
            }
            var result = new string[numArgs];

            for (int i = 0; i < numArgs; i++)
            {
               IntPtr currArg = Marshal.ReadIntPtr(argv, i * Marshal.SizeOf(typeof(IntPtr)));
               result[i] = Marshal.PtrToStringUni(currArg);
            }

            return result;
         }
         finally
         {

            _LocalFree(argv);
         }
      }

   }

   public interface ISingleInstanceApp
   {
      bool SignalExternalCommandLineArgs(IList<string> args);
   }

   /// <summary>
   /// This class checks to make sure that only one instance of 
   /// this application is running at a time.
   /// </summary>
   /// <remarks>
   /// Note: this class should be used with some caution, because it does no
   /// security checking. For example, if one instance of an app that uses this class
   /// is running as Administrator, any other instance, even if it is not
   /// running as Administrator, can activate it with command line arguments.
   /// For most apps, this will not be much of an issue.
   /// </remarks>
   public static class SingleInstance<TApplication>
               where TApplication : Application, ISingleInstanceApp
   {
      #region Private Fields

      /// <summary>
      /// String delimiter used in channel names.
      /// </summary>
      private const string Delimiter = ":";

      /// <summary>
      /// Suffix to the channel name.
      /// </summary>
      private const string ChannelNameSuffix = "SingeInstanceIPCChannel";

      /// <summary>
      /// Remote service name.
      /// </summary>
      private const string RemoteServiceName = "SingleInstanceApplicationService";

      /// <summary>
      /// IPC protocol used (string).
      /// </summary>
      private const string IpcProtocol = "ipc://";

      /// <summary>
      /// Application mutex.
      /// </summary>
      private static Mutex singleInstanceMutex;

      /// <summary>
      /// IPC channel for communications.
      /// </summary>
      private static IpcServerChannel channel;

      /// <summary>
      /// List of command line arguments for the application.
      /// </summary>
      private static IList<string> commandLineArgs;

      #endregion

      #region Public Properties

      /// <summary>
      /// Gets list of command line arguments for the application.
      /// </summary>
      public static IList<string> CommandLineArgs
      {
         get { return commandLineArgs; }
      }

      #endregion

      #region Public Methods

      /// <summary>
      /// Checks if the instance of the application attempting to start is the first instance. 
      /// If not, activates the first instance.
      /// </summary>
      /// <returns>True if this is the first instance of the application.</returns>
      [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1000:DoNotDeclareStaticMembersOnGenericTypes")]
      public static bool InitializeAsFirstInstance(string uniqueName)
      {
         commandLineArgs = GetCommandLineArgs(uniqueName);

         // Build unique application Id and the IPC channel name.
         string applicationIdentifier = uniqueName + Environment.UserName;

         string channelName = String.Concat(applicationIdentifier, Delimiter, ChannelNameSuffix);

         // Create mutex based on unique application Id to check if this is the first instance of the application. 
         bool firstInstance;
         singleInstanceMutex = new Mutex(true, applicationIdentifier, out firstInstance);
         if (firstInstance)
         {
            CreateRemoteService(channelName);
         }
         else
         {
            SignalFirstInstance(channelName, commandLineArgs);
         }

         return firstInstance;
      }

      /// <summary>
      /// Cleans up single-instance code, clearing shared resources, mutexes, etc.
      /// </summary>
      [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1000:DoNotDeclareStaticMembersOnGenericTypes")]
      public static void Cleanup()
      {
         if (singleInstanceMutex != null)
         {
            singleInstanceMutex.Close();
            singleInstanceMutex = null;
         }

         if (channel != null)
         {
            ChannelServices.UnregisterChannel(channel);
            channel = null;
         }
      }

      #endregion

      #region Private Methods

      /// <summary>
      /// Gets command line args - for ClickOnce deployed applications, command line args may not be passed directly, they have to be retrieved.
      /// </summary>
      /// <returns>List of command line arg strings.</returns>
      private static IList<string> GetCommandLineArgs(string uniqueApplicationName)
      {
         string[] args = null;
         if (AppDomain.CurrentDomain.ActivationContext == null)
         {
            // The application was not clickonce deployed, get args from standard API's
            args = Environment.GetCommandLineArgs();
         }
         else
         {
            // The application was clickonce deployed
            // Clickonce deployed apps cannot recieve traditional commandline arguments
            // As a workaround commandline arguments can be written to a shared location before 
            // the app is launched and the app can obtain its commandline arguments from the 
            // shared location               
            string appFolderPath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), uniqueApplicationName);

            string cmdLinePath = Path.Combine(appFolderPath, "cmdline.txt");
            if (File.Exists(cmdLinePath))
            {
               try
               {
                  using (TextReader reader = new StreamReader(cmdLinePath, System.Text.Encoding.Unicode))
                  {
                     args = NativeMethods.CommandLineToArgvW(reader.ReadToEnd());
                  }

                  File.Delete(cmdLinePath);
               }
               catch (IOException)
               {
               }
            }
         }

         if (args == null)
         {
            args = new string[] { };
         }

         return new List<string>(args);
      }

      /// <summary>
      /// Creates a remote service for communication.
      /// </summary>
      /// <param name="channelName">Application's IPC channel name.</param>
      private static void CreateRemoteService(string channelName)
      {
         BinaryServerFormatterSinkProvider serverProvider = new BinaryServerFormatterSinkProvider();
         serverProvider.TypeFilterLevel = TypeFilterLevel.Full;
         IDictionary props = new Dictionary<string, string>();

         props["name"] = channelName;
         props["portName"] = channelName;
         props["exclusiveAddressUse"] = "false";

         // Create the IPC Server channel with the channel properties
         channel = new IpcServerChannel(props, serverProvider);

         // Register the channel with the channel services
         ChannelServices.RegisterChannel(channel, true);

         // Expose the remote service with the REMOTE_SERVICE_NAME
         IPCRemoteService remoteService = new IPCRemoteService();
         RemotingServices.Marshal(remoteService, RemoteServiceName);
      }

      /// <summary>
      /// Creates a client channel and obtains a reference to the remoting service exposed by the server - 
      /// in this case, the remoting service exposed by the first instance. Calls a function of the remoting service 
      /// class to pass on command line arguments from the second instance to the first and cause it to activate itself.
      /// </summary>
      /// <param name="channelName">Application's IPC channel name.</param>
      /// <param name="args">
      /// Command line arguments for the second instance, passed to the first instance to take appropriate action.
      /// </param>
      private static void SignalFirstInstance(string channelName, IList<string> args)
      {
         IpcClientChannel secondInstanceChannel = new IpcClientChannel();
         ChannelServices.RegisterChannel(secondInstanceChannel, true);

         string remotingServiceUrl = IpcProtocol + channelName + "/" + RemoteServiceName;

         // Obtain a reference to the remoting service exposed by the server i.e the first instance of the application
         IPCRemoteService firstInstanceRemoteServiceReference = (IPCRemoteService)RemotingServices.Connect(typeof(IPCRemoteService), remotingServiceUrl);

         // Check that the remote service exists, in some cases the first instance may not yet have created one, in which case
         // the second instance should just exit
         if (firstInstanceRemoteServiceReference != null)
         {
            // Invoke a method of the remote service exposed by the first instance passing on the command line
            // arguments and causing the first instance to activate itself
            firstInstanceRemoteServiceReference.InvokeFirstInstance(args);
         }
      }

      /// <summary>
      /// Callback for activating first instance of the application.
      /// </summary>
      /// <param name="arg">Callback argument.</param>
      /// <returns>Always null.</returns>
      private static object ActivateFirstInstanceCallback(object arg)
      {
         // Get command line args to be passed to first instance
         IList<string> args = arg as IList<string>;
         ActivateFirstInstance(args);
         return null;
      }

      /// <summary>
      /// Activates the first instance of the application with arguments from a second instance.
      /// </summary>
      /// <param name="args">List of arguments to supply the first instance of the application.</param>
      private static void ActivateFirstInstance(IList<string> args)
      {
         // Set main window state and process command line args
         if (Application.Current == null)
         {
            return;
         }

         ((TApplication)Application.Current).SignalExternalCommandLineArgs(args);
      }

      #endregion

      #region Private Classes

      /// <summary>
      /// Remoting service class which is exposed by the server i.e the first instance and called by the second instance
      /// to pass on the command line arguments to the first instance and cause it to activate itself.
      /// </summary>
      private class IPCRemoteService : MarshalByRefObject
      {
         /// <summary>
         /// Activates the first instance of the application.
         /// </summary>
         /// <param name="args">List of arguments to pass to the first instance.</param>
         public void InvokeFirstInstance(IList<string> args)
         {
            if (Application.Current != null)
            {
               // Do an asynchronous call to ActivateFirstInstance function
               Application.Current.Dispatcher.BeginInvoke(
                   DispatcherPriority.Normal, new DispatcherOperationCallback(SingleInstance<TApplication>.ActivateFirstInstanceCallback), args);
            }
         }

         /// <summary>
         /// Remoting Object's ease expires after every 5 minutes by default. We need to override the InitializeLifetimeService class
         /// to ensure that lease never expires.
         /// </summary>
         /// <returns>Always null.</returns>
         public override object InitializeLifetimeService()
         {
            return null;
         }
      }

      #endregion
   }
}
